Vapor-electric device



Nov. 3, 1942. P. L LENz 2,300,941

VAPORfELECTRIC DEVICE *www ATTORNEY 2 Sheets-Sheet 2 l INVENTOR Pezer L. Lenz.

ATTORNEY P. l.. LENz vAPon-ELEcTnIc DEVICE Filed 'July 2o, 1940 Nov. 3, 1942.

WITNESSES:

Patented Nov. 3, 1942 VAPOR-ELECTRIC DEVICE Peter L. Lenz, Edgewood, Pa., as signor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsyl- Application July 20, 1940, Serial No. 346,539

' (cl. 25o-27.5)

8 Claims.

My invention relates to a vapor-electric device and, particularly, to a lead-in bushing for the low current leads of such a device.

In the operation of vapor-electric devices, such as mercury arc converters, it is desirable to provide one or more auxiliary entrance bushings for supplying power to the control electrodes of the device. Heretofore, such auxiliary entrance bushings have been substantially miniatures of the main entrance bushings such as are used for making connections to the main electrodes of such electric valves. These miniatures or auxiliary bushings have heretofore cost approximately $7.50 each, and frequently two or more -of these auxiliary bushings are required for each of the main electrodes of the vapor-electric deon the cathode.

vice, the auxiliary lead-ins appreciably increasing the cost of the iinished device.

According to my invention auxiliary bushings of substantially the size and shape of ordinary spark plugs are utilized for making the auxiliary lead-in connections. The bushings according to my invention can be produced and installed for approximately 75 cents each, thereby effecting a material saving in the overall construction cost of the vapor-electric valve.

The bushing according to my invention has a suitable conducting core spaced from a shell, a portion of which shell can be threaded into a threaded opening in the container of `the vaporelectric device, the threads being sufficiently tight to prevent the passage of mercury alongside the thread, while the vacuum-tight joint is made by suitable deformable gaskets retained between a portion of the bushing and a cooperating portion of the container in which the bushing is inserted.

It is, therefore, an object of my invention to provide a safe and dependable entrance bushing for the auxiliary leads of a vapor-electric device.

Other objects and advantages of my invention will be apparent from the following detailed description taken in conjunction With the accompanying drawings, in which:

y Figure 1 is a sectional elevation of a vaporelectric converter showing an entrance bushing according to my invention; and

Fig. 2 is an enlarged section showing the details of an entrance bushing according to my invention.

In the illustrative embodiment of my invention,` a vapor-electric device is shown as a mercury-arc valve having a metallic container I which can be evacuated to provide the necessary low working pressure for the device. In the bottomof the container 1I is a suitable vaporizable cathode 2 usually constructed of mercury or mercury amalgam. Cooperating with the cathode 2 is a main anode 3 for carrying the main working current of the device. Contacting with the cathode 2 is a suitable make-alive electrode 4 for periodically initiating a cathode spot A lead-in connection 5 is attached to this make-alive electrode 4 and is con- ,ducted through the side wall of the container I by means of my improved bushing presently to be described.

A suitable hole or opening 5 is provided in the wall of the container I, preferably in a cornparatively heavy portion such as the upper rim 1 or top 8 of the container I. However, it is obvious that this opening can be placed any place that is desired and, if necessary, the side wall of the container I may be built up by welding on, or otherwise increasing the thickness of metal to provide suiiicient space for a threaded portion 9 which receives a complementary threaded portion I0 on a nut or shell II forming the exterior of my auxiliary bushing. Where the auxiliary bushing is placed in the relatively thick portion of the container, the inner end of the opening 6 is preferably reamed out or otherwise enlarged to provide a restricted chamber between the lead-in 5 and the sides of the opening. Also, this reamed--out portion serves an additional purpose in that it provides a sloping surface so that any mercury which is condensed in the bushing opening 6 Will vdrain back into the container. The draining function may also be secured by drilling the opening yat a slight angle with respect to the side wall. The bushing is provided with a suitable core I5 of conducting material of any size which may be necessary to conduct the current for the auxiliary electrode. I have found that a rod of approximately l-Sg diameter is very satisfactory. The lead-ins are then connected in any suitable manner to the opposite ends of the conducting core I5. I have found that this may be very satisfactorily accomplished by threading the ends of the core I5 and providing a pair of nuts Iii and locking the lead-in wire Il between these nuts. The conducting core I5 is separated from the shell II of the bushing by a suitable insulating body I8 which is connected in vacuum-.tight relation to both the core I5 and the shell li.

While various types of insulating material such as mica, Micalex, ceramic or vitreous material may be used for this ir1sula.ting:body,r rI have shown in Fig. 2 an embodiment utilizing a vitreous insulatingbody I3. To construct this bushing the core I5 is preferably coated with a relatively thin layer of vitreous material over any desired length, and a tubular member 2| capable of tting over the coated core is then sealed in vacuum-tight relation to a relatively thin portion 22 of the metal shell I I. 1f desired, the shell can be made from several portions which are later welded or otherwise connected together to make a unitary structure or, obviously, it could be made originally as a unitary piece. The two vitreous portions 2li and 2I are then assembled and fused together to make a unitary insulating body I8 sealed in vacuumtight relation to both the core I5 and the external shell II. A portion of the external shell II is enlarged to provide a nut-like surface 25 for the engagement of a suitable wrench for screwing the bushing into rm engagement with the threaded portion 9 of the opening 6 in the container Wall. In order to make a vacuumtight seal this complementary threaded portion should be sui'liciently tight to prevent the passage of mercury alongside the threaded port-ions but not necessarily suiiciently tight to prevent the passage of gases therethrough. A suitable seat 26 is then provided on the exterior surface of the container I and a complementary seat 2'! is provided on the enlarged portion of the bushing sleeve II adjacent the threaded portion lil of the sleeve and a suitable compressible gasket 28 which may be either rubber, a soft metal, such as copper or aluminum, or a metal-covered packing material, is inserted between the complementary seats 26 and 2'! and the bushing screwed down suiciently tight to produce a vacuum-tight seal by deforming the gasket 28 into intimate contact with the complementary seats 2B and 21.

While for purposes of illustration I have shown and described a specific embodiment of my invention, it will be apparent that changes and modifications can be made therein without departing from the true spirit of my invention or the scope of the appended claims.

I claim as my invention:

1. A lead-in construction for an auxiliary connection of a mercury vapor device comprising a wire-like lead-in conductor of a metal substantially unaifected by mercury, a vitreous coating fused on a portion of said conductor, a substantially tubular bushing shell, a portion of said shell being of a material readily sealed to the vitreous material, a vitreous body sealed to said portion of said shell and said vitreous coating,

a container for said mercury-vapor device,

threaded means for securing said shell in mercury-tight relation in said container and gasket means for securing vacuum-tight connection between said shell and said container.

2. A vaporizable-cathode mercury-vapor arcdevice comprising an evacuated metal container having a mercury cathode therein, means for producing an arc within said container, said container providing means for condensing the mercury vaporized by said arc, said container having a threaded opening therein at a mercurycondensing point removed from the immediate vicinity of the arc, and a terminal-bushing having an externally threaded metal nut screwed in said threaded opening; said nut making a substantially vacuum-tight joint with said evacuated container; said terminal-bushing having a single centrally disposed lead-in conductor-Wire and a solid insulating sleeve tightly surrounding said lead-in conductor-wire in such manner as to make a substantially vacuum-tight joint therewith, said insulating sleeve being disposed between said wire and the bore of said nut, the portion of the sleeve which is disposed Within the bore of the nut fitting tightly therein in such manner as to make a substantially vacuum-tight joint therewith; said insulating sleeve having an inner portion adjoining the nut-engaging portion and extending over the inwardly extending portion of the lead-in wire, within the evacuated container, said inner portion of the insulating sleeve having an exposed insulating surface extending inwardly from the nut to provide an adequate insulating creepage-distance for the droplets of condensate mercury; and said container, nut, lead-in wire, and inner portion of the insulating sleeve all being of materials which are not deleteriously attacked by mercury to any substantial extent.

3. A vaporizable-cathode mercury-vapor arcdevice comprising an evacuated metal container having a mercury cathode therein, means for producing an arc within said container, said container providing means for condensing the mercury vaporized by said arc, said container having a threaded opening therein at a mercurycondensing point removed from the immediate vicinity of the arc, and a terminal-bushing having an externally threaded portion screwed in said threaded opening, said terminal-bushing making a substantially vacuum-tight joint with said evacuated container; said terminal-bushing having a single centrally disposed lead-in conductor-wire, an insulating sleeve tightly surrounding said lead-in conductor-wire, and inner and outer conductor-connecting means on the respective inner and outer ends of the lead-in conductor-wire for connection to the inner and outer portions of a terminal conductor of said arc-device; said insulating sleeve making a substantially vacuum-tight seal between said threaded portion and the wire; said insulating sleeve extending over the inwardly extending portion of said lead-in wire for a substantial distance from said screwed-in threaded portion to provide an adequate insulating oreepage-surface for preventing the condensed mercury from causing the formation of a conducting path between the inner end of the lead-in Wire and the metal container; and said container, said lead-in wire, said threaded portion, said creepage surface of the insulating sleeve, and said inner conductorconnecting means all being of materials which are not deleteriously attacked by mercury to any substantial extent.

4. A vaporizable-cathode mercury-vapor arcdevice comprising an evacuated metal container having a mercury cathode therein, means for producing an arc within said container, said container providing means for condensing the mercury vaporized by said arc, said container having a threaded opening therein at a mercurycondensing point removed from the immediate vicinity of the arc, and a terminal-bushing having an externally threaded portion screwed in said threaded opening, said terminal-bushing making a substantially vacuum-tight joint with said evacuated container; said terminal-bushing having a single centrally disposed lead-in conductor-wire and a solid insulating sleeve tightly surrounding said lead-in conductor-wire; said insulating sleeve making a substantially vacuumtight seal between said threaded portion and the wire; said insulating sleeve extending over the inwardly extending portion of said lead-in wire for a substantial distance from said screwed-in threaded portion to provide an adequate insulating creepage-surface for preventing the condensed mercury from causing the formation of a conducting path between the inner end of the lead-in wire and the metal container; said container having means surrounding the inner end of the threaded opening for providing a restricted chamber surrounding the adjacent portion of said creepage-surface in closely spaced separation therefrom; and said container, said lead-in Wire, said threaded portion, and said creepage-surface of the insulating sleeve all being of materials which are not deleteriously attacked by mercury to any substantial extent.

5. A terminal-bushing comprising an externally threaded metal nut, a single centrally disposed lead-in conductor-wire and a solid insulating sleeve tightly surrounding said lead-in conductor-Wire in such manner as to make a substantially vacuum-tight joint therewith, said in sulating sleeve being disposed between said wire and the bore of said nut, the portion of the sleeve which is disposed within the bone of the nut iitting tightly therein in such manner as to make a substantially vacuum-tight joint therewith; said insulating sleeve having a guard-portion adjoining the nut-engaging portion and extending over a portion 0f the lead-in wire of the bushing, said guard-portion of the insulated sleeve having an exposed insulating surface extending inwardly from the nut to provide a substantial insulating creepage-surface; and said nut, lead-in wire, and guard-portion of the insulating sleeve all being of materials which are not deleteriously attacked by mercury to any substantial extent.

6. A terminal-bushing comprising an externally threaded joint-making portion, said terminal-bushing having a single centrally disposed lead-in conductor-wire, a solid insulating sleeve tightly surrounding said lead-in conductor-Wire, and inner and outer conductor-connecting means on the respective inner and outer ends of the lead-in conductor-Wire; said insulating sleeve making a substantially vacuum-tight seal between said threaded portion and the wire; said insulating sleeve extending over a portion of said lead-in wire for a substantial distance from said threaded joint-making portion to provide an insulating creepage-surface; said lead-in wire, said threaded portion, said creepage surface of the insulating sleeve, and said inner conductor-connecting means all being of materials which are not deleteriously attacked by mercury to any substantial extent.

'7. vApparatus comprising a metal container having a threaded opening therein, and a terminal-bushing having an externally threaded portion screwed in said threaded opening, said terminal-bushing making a substantially vacuum-tight joint with said container; said terminal-bushing having a single centrally disposed lead-in conductor-wire and a solid insulating sleeve tightly surrounding said lead-in'conductor-wire; said insulating sleeve making a substantially vacuum-tight seal between said threaded portionl and the Wire; said insulating sleeve extending over the inwardly extending portion of said lead-in wire for a substantial distance from said screwed-in threaded portion to provide an adequate insulating creepage-surface; and said container having means surrounding the inner end of the threaded opening for providing a restricted chamber surrounding the adjacent portion of said creepage-surface in closely spaced separation therefrom.

8. In a mercury arc-discharge device, a lead-in construction comprising a metallic container for said device, an opening in said container at a position spaced from the arc-discharge, a conductor extending through said opening, a bushing shell in threaded engagement with said opening, an insulating body surrounding said conductor, said insulating body being sealed in vacuumtight relation to said conductor and to said shell, said insulating body extending axially beyond the end of the shell at each end of the shell, means for establishing electrical connections to each end of said conductor, and means for making a vacuum-tight seal between said shell and said container.

PETER L. LENZ. 

